The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 05, 1998
Filed:
Jul. 28, 1995
Jeffrey T Kelley, Plymouth, MI (US);
Bruce Wrenbeck, Dearborn, MI (US);
United Technologies Automotive, Inc., Dearborn, MI (US);
Abstract
A pulse width modulation circuit includes a transistor pass element alternately switched on and off by an oscillator and connecting a power source to a load. Current through the transistor pass element is compared to a reference signal by a comparator. If the current through the transistor pass element exceeds the reference signal, the comparator generates a fault signal, and the transistor pass element is switched off for the remainder of the cycle. After a predetermined number of faults, the transistor pass element is switched off for a plurality of cycles. The pulse width modulation circuit prevents damage to the transistor pass element caused by the low initial resistance of the load and supplies sufficient current to slowly heat the load to steady state operation. This also allows for downsizing of the pass element for steady state conditions thereby saving product cost.